Field of the Invention
The present invention relates to a lighting device using an LED as a lighting source, more specifically, to a backlight unit, a liquid crystal display device, and a lamp device for vehicles using the lighting device.
Description of the Related Arts
A device implementing lighting by guiding light emitting at a light source has been variously required for a lamp for lighting, a lamp for vehicles, a liquid crystal display device and the like. In the lighting device, a technology for making the structure of equipment thin, and a structure capable of improving light efficiency have been recognized as the most important technologies.
As one example in which the lighting device is operated, a liquid crystal display device is explained as follows.
Referring to FIG. 1, the lighting device 1 is configured such that a flat light guide plate 30 is disposed on a substrate 20, and a plurality of side-view LEDs 10 (showing only one LED) are disposed in an array type on a side surface of the light guide plate 30.
In the LEDs 10, light L incident to the light guide plate 30 is reflected upward by a fine reflective pattern or a reflection sheet 40 provided a bottom surface of the light guide plate and is emitted from the light guide plate 30. Thereafter, the light is provided to an LCD panel 50 of an upper part of the light guide plate 30.
Like a conceptual view illustrated in FIG. 2, the lighting device may be formed in a structure in which a plurality of optical sheets such as an optical sheet 31, prism sheets 32 and 33, and a protective sheet 34, or the like, are further added between the light guide plate 30 and the LCD panel 50.
Accordingly, the light guide plate is basically used as an essential component of the lighting device. However, due to a thickness of the light guide plate itself, there is a limitation to make a whole thickness of a product thin. In the case of a large-scaled lighting device, it is problematic that image quality is deteriorated.